The surface soil hydrology is extremely important for driving the formation and evolution of vegetation patches in water-limited ecosystems. However, the process of soil hydrology and its response to vegetation patches are unclear due to limited tools. This study chose patchy grass Achnatherum splendens as an indicator plant to reveal the spatial-temporal dynamics of soil water and salt, and soil water and salt responses to spatial patterns of A. splendens patches, were shown by electrical conductivity (ECa) images, in the study area of Qinghai Lake watershed in north-western China. The results showed that there were significant positive correlations (P<0.01) between ECa, and soil water and salt. ECa could be used as a proxy for the changes of soil water and salt, because soil water and salt could explain 81% of the ECa changes based on the multivariate regression model. Moreover, based on the time-lapse ECa images, the increment of soil water under A. splendens patches was higher than that of matrix zones, compared with before and after intensive rainfall, meaning A. splendens patches acted as sink to accumulate water runoff. Analysis of temporal stability showed spatial ECa patterns were highly consistent with the distributions of A. splendens patches, and soil water and salt content under A. splendens patches were remarkable higher than that of matrix zones, whatever the moist conditions or seasons. This indicated that A. splendens patches were the accumulation area for soil water and salt. Therefore, the findings of this study proved that it is a novel method to reveal the dynamics of soil water and salt, and its responses to the spatial patterns of A. splendens patches by EMI method, which might provide valuable insights in understating the hydrological process of patchy vegetation.